diff --git a/package/pkg-cargo.mk b/package/pkg-cargo.mk
index 264bf5a1ae..7802c3a883 100644
--- a/package/pkg-cargo.mk
+++ b/package/pkg-cargo.mk
@@ -96,8 +96,12 @@ $(2)_DL_ENV += BR_CARGO_MANIFEST_PATH=$$($(2)_SUBDIR)/Cargo.toml
 endif
 
 # Due to vendoring, it is pretty likely that not all licenses are
-# listed in <pkg>_LICENSE.
+# listed in <pkg>_LICENSE. If the license is unset, it is "unknown"
+# so adding unknowns to some unknown is still some other unkown,
+# so don't append the blurb in that case.
+ifneq ($$($(2)_LICENSE),)
 $(2)_LICENSE += , vendored dependencies licenses probably not listed
+endif
 
 # Note: in all the steps below, we "cd" into the build directory to
 # execute the "cargo" tool instead of passing $(@D)/Cargo.toml as the